This invention relates to plasma devices.
It is well known that in plasma devices such as reactors for thermonuclear fusion one problem in the containment of the plasma is the damage resulting from bombardment of exposed surfaces by energetic atoms or ions. Such bombardment causes implantation of atoms especially atoms of helium or of isotopes of hydrogen, in the surfaces of walls or other components exposed to the plasma. The implanted material collects and forms blisters that erode the exposed surface, threatening structural integrity. Broken blisters also produce impurities in the form of particles released from the wall and are ejected into the plasma.
One method of reducing the effects of helium blistering in such structures as the first wall or the diverter of a fusion reactor is to heat the structure to about half its melting temperature. This tends to drive helium out from the surface before it collects to form the large bubbles that result in surface erosion and contamination. However, maintaining such a temperature is likely to be a difficult problem in the components that are to be prevented from blistering, may reduce excessively the strength of these components, and may threaten thermal damage to other nearby components. Also, the chemical corrosion of the component by liquid coolant (e.g. liquid lithium) will be severe at these high temperatures. For example, the temperature needed for materials such as niobium and vanadium is in excess of 1100 K.
Another method of reducing the effects of plasma contamination due to helium blistering is to use materials of low atomic number (low Z). This minimizes the effect of contamination per released atom. However, many low-Z materials cannot be heated sufficiently in their normal forms to the temperatures needed to reduce blistering without losing mechanical and structural integrity.
It is an object of the present invention to provide a better coating for components in the interior of a plasma device.
It is a further object of the present invention to provide a method of minimizing damage due to helium blistering on components inside a fusion reactor.
It is a further object of the present invention to avoid the need for continuous heating of interior walls of a plasma device for the purpose of reduction of surface erosion.
Other objects will become apparent in the course of a detailed description of the invention.